1. Field of the Invention
The present invention relates to a toroidal continuously variable transmission used for a vehicle.
2. Description of the Related Art
Japanese Utility Model Unexamined Publication No. 58(1983)-112762 discloses a toroidal continuously variable transmission using a conical roller bearing having a conical roller as a rolling element. In this publication, the toroidal continuously variable transmission has a first contact made between the conical roller and an inner wheel orbital face, and a second contact made between the conical roller and an outer wheel orbital face. Being a line contact, each of the first contact and the second contact is high in rigidity, thus causing ununiformity in load applied to the rolling element of the bearing of a power roller of the toroidal continuously variable transmission.
It is an object of the present invention to provide a toroidal continuously variable transmission with an enhanced durability of a bearing of a power roller. To enhance the durability of the bearing of the power roller, ununiformity in load applied to the rolling element is redressed by reducing rigidity of a contact between a rolling element and a wheel orbital face.
According to a first aspect of the present invention, there is provided a toroidal continuously variable transmission comprising:
1) a first input disc formed with a toroidal groove;
2) a second input disc formed with a toroidal groove;
3) an output disc formed with:
a first toroidal groove opposed to the toroidal groove of the first input disc, and
a second toroidal groove opposed to the toroidal groove of the second input disc;
4) a trunnion; and
5) a plurality of power rollers each of which is interposed in one of the positions including the following;
I) between a wall of the toroidal groove of the first input disc and a wall of the first toroidal groove of the output disc, and
II) between a wall of the toroidal groove of the second input disc and a wall of the second toroidal groove of the output disc,
each of the power rollers being gyratorily held with the trunnion,
each of the power rollers comprising;
i) an inner wheel for transmitting a power of one of the first input disc and the second input disc to the output disc,
ii) an outer wheel held with the trunnion, and
iii) a power roller bearing for bearing the inner wheel in such a manner that the inner wheel rotates relative to the outer wheel, the power roller bearing comprising;
A) an inner wheel orbital face formed on the inner wheel,
B) an outer wheel orbital face formed on the outer wheel, and
C) a rolling element interposed between the inner wheel orbital face and the outer wheel orbital face, the rolling element being shaped substantially into a frustum of a cone, a point contact being made between one of the following while a line contact being made between the other of the following:
a) the rolling element and the inner wheel orbital face, and
b) the rolling element and the outer wheel orbital face.
According to a second aspect of the present invention, there is provided a toroidal continuously variable transmission comprising:
1) a first input disc formed with a toroidal groove;
2) a second input disc formed with a toroidal groove;
3) an output disc formed with:
a first toroidal groove opposed to the toroidal groove of the first input disc, and
a second toroidal groove opposed to the toroidal groove of the second input disc;
4) a trunnion; and
5) a plurality of power rollers each of which is interposed in one of the positions including the following;
I) between a wall of the toroidal groove of the first input disc and a wall of the first toroidal groove of the output disc, and
II) between a wall of the toroidal groove of the second input disc and a wall of the second toroidal groove of the output disc,
each of the power rollers being gyratorily held with the trunnion,
each of the power rollers comprising;
i) an inner wheel for transmitting a power of one of the first input disc and the second input disc to the output disc,
ii) an outer wheel held with the trunnion, and
iii) a power roller bearing for bearing the inner wheel in such a manner that the inner wheel rotates relative to the outer wheel, the power roller bearing comprising;
A) an inner wheel orbital face formed on the inner wheel,
B) an outer wheel orbital face formed on the outer wheel, and
C) a rolling element interposed between the inner wheel orbital face and the outer wheel orbital face, the rolling element being shaped substantially into a frustum of a cone, a first contact width being made between one of the following while a second contact width greater than the first contact width being made between the other of the following:
a) the rolling element and the inner wheel orbital face, and
b) the rolling element and the outer wheel orbital face.
According to a third aspect of the present invention, there is provide a power roller for a toroidal continuously variable transmission, the power roller comprising:
i) an inner wheel for transmitting a power of an input disc (3, 4) to an output disc,
ii) an outer wheel held with a trunnion, and
iii) a power roller bearing for bearing the inner wheel in such a manner that the inner wheel rotates relative to the outer wheel, the power roller bearing comprising;
A) an inner wheel orbital face formed on the inner wheel,
B) an outer wheel orbital face formed on the outer wheel, and
C) a rolling element interposed between the inner wheel orbital face and the outer wheel orbital face, the rolling element being shaped substantially into a frustum of a cone, a first contact being made between one of the following while a second contact being made between the other of the following:
a) the rolling element and the inner wheel orbital face, and
b) the rolling element and the outer wheel orbital face.
According to a fourth aspect of the present invention, there is provided a power roller for a toroidal continuously variable transmission, the power roller comprising:
i) an inner wheel for transmitting a power of an input disc (3, 4) to an output disc,
ii) an outer wheel held with a trunnion, and
iii) a power roller bearing for bearing the inner wheel in such a manner that the inner wheel rotates relative to the outer wheel, the power roller bearing comprising;
A) an inner wheel orbital face formed on the inner wheel,
B) an outer wheel orbital face formed on the outer wheel, and
C) a rolling element interposed between the inner wheel orbital face and the outer wheel orbital face, the rolling element being shaped substantially into a frustum of a cone, a first contact width being made between one of the following while a second contact width greater than the first contact width being made between the other of the following:
a) the rolling element and the inner wheel orbital face, and
b) the rolling element and the outer wheel orbital face.
The other objects and features of the present invention will become understood from the following description with reference to the accompanying drawings.